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|Title:||Combined effect of UV-B and heat shock on photosynthetic apparatus of wild type and UV -B-HS-tolerant (UV -HSt) mutant strain of cyanobacterium Anacystis nidulans|
|Authors:||Bisen, P S|
Gour, R K
|Abstract:||Ultraviolet-B (UV-B) and heat shock (HS) induced changes in the photosynthetic apparatus have been studied in the wild type A. nidulans and its ultraviolet-heat shock tolerant (UV-HSt) mutant strain. Application of the UV -B and HS stresses either separately or in combination showed a drastic photobleaching and alteration in the ratio of phycocyan in and chlorophyll a (PC/Chl a) in the wild type strain as compared to its UV-HSt mutant counterpart. Both wild type and UV-HSt mutant strain exhibited similar rate of photosynthetic O2 evolution at fluorescent high light irradiance (30 Wm-2) , however, the photosynthetic yield in UV-HSt mutant strain was 28 fold higher than that of its wild type counterpart. Further, the wild type strain showed UV-B/HS dose-dependent inhibition in the photosynthetic electron transport chain and maximum inhibition was recorded at 5 Wm-2 of UV -B and 40°C of heat shock. In contrast, UV -HSt mutant strain showed slight enhancement in its photosynthetic activities at 1 Wm-2 of UV-B or 35°C of HS and after that followed a decreasing pattern. The ratio of PS II/PS I in wild type strain increased significantly with dose-dependent increment in UV -B or heat-shock, whereas such changes were found to be insignificant in the UV-HSt mutant strain. Furthermore, the data ascertained the role of different temperature in recovery of UV-HS- induced damage in presence and absence of light as the high temperature (35°C) contributed the maximum recovery of Hill activity in UV-HSt mutant strain, whereas, the wild type strain recovered at low temperature (25°C).|
|ISSN:||0975-1009 (Online); 0019-5189 (Print)|
|Appears in Collections:|| IJEB Vol.37(06) [June 1999]|
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